Block copolymers of styrene or 2-vinylpyridine and ethylene oxide are known (Encyclopedia of Polymer Science and Engineering 2, 334). They are obtained in a two-step method by synthesizing the vinyl block A in first step by anionic polymerization of the vinyl compounds in the presence of alkyl or arylalkyl compounds, such as butyl lithium. This vinyl block A is then reacted in second step with alkylene oxide via an addition reaction.
The method of anionic polymerization of the vinyl monomers has, however, several fundamental disadvantages. See, Encyclopedia of Polymer Science and Engineering, 2, 330. Reagents and solvents of high purity have to be used. It is necessary to work in a high vacuum or with a highly purified inert gas. Very low temperatures must be maintained during the anionic polymerization and only a limited number of monomers can be polymerized anionically.
Block copolymers of polystyrene or polyvinylpyridine and alkylene oxides represent an interesting class of surface active compounds, which are described, for example, in Tenside Surf. Det. 28 (1991) 3. They are effective emulsifiers for emulsion polymerization and produce a stable polymer latex with modified surface properties, which cannot easily be achieved using conventional emulsifiers. Using these block polymers, water-soluble monomers, such as acrylamide, can be polymerized in water-in-oil microemulsions.